Blackfly on the runner beans

[The Mouse]

The underside of the leaves is the place where I usually find colonies of blackfly on my runner beans.

So far this year, mine haven't been any worse than usual - I have spotted a couple of badly infested leaves but cleared them using a combination of the squashing method and the hosepipe method. I'm still a bit squeamish, so it feels better if I squash and wash at the same time, as it avoids that horrible sticky finger feeling!

As long as they stay on the leaves, rather than the flower heads, I find that this method works perfectly for me.

[alan refail]

The problem with "natural" predators is that they have to be there to do any good
Has anyone seen more than the occasional ladybird eating the black-fly on their runners?

[Chantal]

Hello! I am new to KG. I live in SW Scotland now and have been an organic gardener for a good while. I have had no blackfly this year and have never seen it on runners - so I guess that they are not the host of choice. Lawrence Hills recommended boiling 3lb of rhubarb leaves and adding soapflakes to the cooled filtrate - to make about a gallon of liquid to spray against aphids in general. It might work with runners if caught early.?

Hi Penny, welcome to the KG Forum

I have a pack of soap flakes somewhere not to mention a lot of rhubarb leaves, so I may well give this a go before things get out of hand. I'm very bored with squishing the things and have now found both blackfly AND greenfly on the tomatoes too The one year that I'm not already spraying for blight and I get aphids instead, although I suspect spraing for blight probably stopped them dead in their tracks!

[Galatea]

As you suggest, petroleum and chemical based detergents can be more harmful than many pesticides. The surfactants are extremely resilient and tough to break down in the environment, whilst anti-bacterial soaps will decimate the vital micro-organisms in your soil.

As well as soft soap you can safely use and vegetable based soap - something like Ecover washing-up liquid, for instance, which is easily and cheaply available and will do the job.

There are also a variety of organic, plant-based solutions that will readily deal with aphids. There's a good article on Ecocharlie with a variety of suggestions:

http://www.ecocharlie.co.uk/blog/index. ... -solutions -

You can but some of the plant-based sprays (I've seen a Garlic-based one recently) but they're easy enough to "home brew" and also have a longer-lasting effect than soap. Plus I like the idea of using the natural defences of one plant (like Chilli, Garlic or Rhubarb) to protect another too.

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[Beryl]

I seem to remember reading recently that ladybird larva and ladybirds need blackfly/aphids to survive and will only visit plants that are infested with bladckfly.

I don't spray with anything and although I have some blackfly I do also have lots of ladybirds.

Perhaps its worth leaving well alone and give it a try.

Beryl.